Process for producing polypropylene from C3 olefins selectively produced by a two stage fluid catalytic cracking process

Abstract

A process for producing polymers from olefins selectively produced by a two stage process for selectively producing C2 to C4 olefins from a gas oil or resid is disclosed herein. The gas oil or resid is reacted in a first stage comprising a fluid catalytic cracking unit wherein it is converted in the presence of conventional large pore zeolitic catalyst to reaction products, including a naphtha boiling range stream. The naphtha boiling range stream is introduced into a second stage comprising a process unit containing a reaction zone, a stripping zone, a catalyst regeneration zone, and a fractionation zone. The naphtha feed is contacted in the reaction zone with a catalyst containing from about 10 to 50 wt. % of a crystalline zeolite having an average pore diameter less than about 0.7 nanometers at reaction conditions which include temperatures ranging from about 500 to 650° C. and a hydrocarbon partial pressure from about 10 to 40 psia. Vapor products are collected overhead and the catalyst particles are passed through the stripping zone on the way to the catalyst regeneration zone. Volatiles are stripped with steam in the stripping zone and the catalyst particles are sent to the catalyst regeneration zone where coke is burned from the catalyst, which is then recycled to the reaction zone.

What is claimed is:  
     
       1. A process for producing polypropylene from C 3  olefins produced in a two stage process for selectively producing C 2  to C 4  olefins from a heavy hydrocarbon feed, the process comprising the steps of: 
       a) contacting a heavy hydrocarbon feed with a large-pore zeolitic catalytic cracking catalyst having an average pore diameter greater than about 0.7 nm in a first reaction stage comprising a fluid catalytic cracking unit to convert the heavy hydrocarbon feed to lower boiling reaction products;  
       b) fractionating said lower boiling reaction products into at least a naphtha boiling range fraction comprising between about 10 and about 30 wt. % paraffins and between about 15 and about 70 wt. % olefins;  
       c) contacting the naphtha boiling range fraction with a second catalyst comprising between about 10 and about 50 wt. % of a crystalline zeolite having an average pore diameter less than about 0.7 nm in a second reaction stage comprising a process unit comprising a reaction zone, a stripping zone, a second catalyst regeneration zone, and a fractionation zone, wherein the naphtha boiling range fraction is contacted with the second catalyst in the reaction zone at reaction conditions which include temperatures ranging from about 500 to 650° C. and a hydrocarbon partial pressure from about 10 to 40 psia and a catalyst to second stage feed weight ratio of about 4 to about 10, and wherein propylene comprises at least about 90 mol. % of the total C 3  product;  
       d) passing catalyst particles through the stripping zone;  
       e) passing the stripped second catalyst particles to the regeneration zone where coke is combusted from the second catalyst;  
       f) recycling the hot catalyst particles to the second stage reaction zone; and,  
       g) separating the propylene and polymerizing the propylene to form polypropylene.  
     
     
       2. The process of claim  1  wherein the crystalline zeolite is selected from the group consisting of ZSM-5 and ZSM-11. 
     
     
       3. The process of claim  2  wherein the reaction temperature is from about 500° C. to about 600° C. 
     
     
       4. The process of claim  3  wherein at least about 60 wt. % of the C 5 + olefins in the naphtha boiling range feed is converted to C 4 − products and less than about 25 wt. % of the paraffins are converted to C 4 − products. 
     
     
       5. The process of claim  4  wherein the weight ratio of propylene to total C 2 − products is greater than about 3.5. 
     
     
       6. The process of claim  1  wherein the large pore zeolitic catalytic cracking catalyst of the first stage is selected from the group consisting of gmelinite, chabazite, dachiardite, clinoptilolite, faujasite, heulandite, analcite, levynite, erionite, sodalite, cancrinite, nepheline, lazurite, scolecite, natrolite, offretite, mesolite, mordenite, brewsterite, ferrierite and the synthetic zeolites X, Y, A, L, ZK-4, ZK-5, B, E, F, H, J, M, Q, T, W, Z, alpha, beta, and omega, and USY. 
     
     
       7. The process of claim  6  wherein the large pore zeolitic catalytic cracking catalyst is a USY zeolite. 
     
     
       8. The process according to claim  1  wherein propylene comprises at least about 95 mol. % of the total C 3  products.